Skip to content

Commit

Permalink
Added concepts for seasonal, conditional ratings (#137)
Browse files Browse the repository at this point in the history 
* Added concepts for seasonal, conditional ratings

* Cleaned up spelling errors

* Update docs/concepts.md

Co-authored-by: Christopher Atkins <57670484+catkins-miso@users.noreply.github.com>
Signed-off-by: Tory McKeag <143734462+getorymckeag@users.noreply.github.com>

* Update cspell.json

Co-authored-by: Christopher Atkins <57670484+catkins-miso@users.noreply.github.com>
Signed-off-by: Tory McKeag <143734462+getorymckeag@users.noreply.github.com>

* Update docs/decision-log/conditional-ratings.md

Co-authored-by: Christopher Atkins <57670484+catkins-miso@users.noreply.github.com>
Signed-off-by: Tory McKeag <143734462+getorymckeag@users.noreply.github.com>

* Update docs/decision-log/conditional-ratings.md

Co-authored-by: Christopher Atkins <57670484+catkins-miso@users.noreply.github.com>
Signed-off-by: Tory McKeag <143734462+getorymckeag@users.noreply.github.com>

* Filled in gaps

* Re-orged concepts

* Update docs/decision-log/seasonal-ratings-schedule.md

Co-authored-by: Christopher Atkins <57670484+catkins-miso@users.noreply.github.com>
Signed-off-by: Tory McKeag <143734462+getorymckeag@users.noreply.github.com>

---------

Signed-off-by: Tory McKeag <143734462+getorymckeag@users.noreply.github.com>
Co-authored-by: Christopher Atkins <57670484+catkins-miso@users.noreply.github.com>
  • Loading branch information
@getorymckeag @catkins-miso
getorymckeag and catkins-miso authored Sep 26, 2024
1 parent 96f2804 commit da622cc
Show file tree
Hide file tree
Showing 7 changed files with 476 additions and 1 deletion.
2 changes: 1 addition & 1 deletion docs/Gemfile.lock
View file
Original file line number Diff line number Diff line change
Expand Up @@ -270,7 +270,7 @@ GEM
concurrent-ruby (~> 1.0)
unicode-display_width (1.8.0)
uri (0.13.1)
webrick (1.8.1)
webrick (1.8.2)

PLATFORMS
x86_64-linux
Expand Down
32 changes: 32 additions & 0 deletions docs/concepts.md
View file
Original file line number Diff line number Diff line change
Expand Up @@ -174,6 +174,24 @@ a distinct data set from Proposals. Proposals may be queried as well as
submitted, so that the rating provider's original input data is always kept
separately from the in-use ratings.

## Seasonal Ratings

Seasonal Line Ratings, or simply Seasonal Ratings in TROLIE, are based on the
formal definition in the pro forma attachment M of FERC order 881, which states:

> (3) "Seasonal Line Rating" means a Transmission Line Rating that:
> (a) Applies to a specified season, where seasons are defined by the Transmission Provider to include not fewer than four seasons in each year, and to reasonably reflect portions of the year where expected high temperatures are relatively consistent.
> (b) Reflects an up-to-date forecast of ambient air temperature across the relevant season over which the rating applies.
> (c) Is calculated annually, if not more frequently, for each season in the future for which Transmission Service can be requested.
Seasonal ratings are used as [Recourse Ratings](#recourse-ratings) in a TROLIE context, as described above. They also may be used for other purposes that go beyond the AAR timeline,
such as planning and other long-term studies.

Seasonal Ratings are defined against [Seasons](#seasons).

## Seasonal Overrides

A seasonal override is submitted by a Ratings Provider in order to instruct the
Expand Down Expand Up @@ -222,3 +240,17 @@ Another typical Monitoring Set would be that which nominates the complete
footprint for the Transmission Provider. A natural choice for the
`monitoring-set` identifier is the NERC id of the entity that defines the
`monitoring-set`, if applicable.

## Seasons

According to pro forma attachment M of FERC 881, a season has the following definition:

> ... where seasons are defined by the Transmission Provider to include not fewer than four seasons in each year, and to reasonably reflect portions of the year where expected high temperatures are relatively consistent.
In practical terms, Transmission Providers have a wide variety of Seasons that they operate to.
Even if seasons across two Transmission Providers have the same name, such as "summer",
the start and end dates may differ. TROLIE is designed to be agnostic to these definitions as much as
possible, so that the data may be exchanged in a more accurate and precise manner. While seasonal "aliases"
such as "winter" may sometimes be provided as hints, seasonal rating schedules are ultimately defined in terms
of start and end dates. Seasonal ratings in TROLIE are represented in terms of start and end dates, and
TROLIE servers may decide how to enforce adherence to specific named seasons that they use.
50 changes: 50 additions & 0 deletions docs/decision-log/conditional-ratings.md
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,50 @@
---
title: Conditional Seasonal Ratings
parent: Decision Records
---

## Status

* Status: `accepted`
* Issue Link: [GitHub Issue](https://github.com/trolie/spec/issues/129)

## Context

There are certain transmission lines that can have different ratings depending on their
configuration. A commonly cited example is underwater lines with cables packed tightly in
trays, where certain combinations of the conductors may be turned on and off. Switching
conductors on and off obviously changes the amount of copper that can carry
electrons. However, to add additional complexity, the wires are close enough together
that they can heat each other up as well, and the overall rating must take this into
account. Therefore, each possible combination will have a unique rating.

When computing AARs however, it is necessary to take the configuration into account
so that the AAR accounts for the actual or forecasted configuration of the line. Therefore,
no special accommodation needs to be considered for AAR exchange in TROLIE.

However, for seasonal ratings, the configuration of the line cannot be
forecasted accurately for use as a recourse rating. A separate rating must be
provided for each configuration, so that the right rating may be used based on the
configuration of the line.

This decision records a strategy for these "conditional" ratings in TROLIE.

## Decision

TROLIE will contain no specific schema elements to represent conditional ratings.
For lines that require conditional ratings, TROLIE servers must expose unique
resource identifiers representing each condition / permutation of the configuration.

This follows from the similar precedent set by the decision
for [directional ratings](directional-ratings.md).

### Conditional-Resource Naming
Much like the problem in naming directional ratings, there is currently no consistent
approach as to how these "conditions" are represented. TROLIE implementations will
be left on their own to implement a convention for these names, likely concatenating
the facility ID with an ID for each possible condition.


## Consequences

An example is provided in [the seasonal ratings examples](../example-narratives/seasonal-ratings.md).
81 changes: 81 additions & 0 deletions docs/decision-log/seasonal-ratings-schedule.md
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,81 @@
---
title: Seasonal Ratings
parent: Decision Records
---

## Status

* Status: `accepted`
* Issue Link: [GitHub Issue](https://github.com/trolie/spec/issues/14)

## Context

While the primary focus of FERC 881 is AARs, the [seasonal ratings](../concepts.md#seasonal-ratings)
still play an important role. In practice, these are used in planning and other non-operational studies
in addition to their role as recourse ratings in operations.

Today, seasonal ratings are managed using various tools, and often tied to network model update processes. For various
reasons, many of these tools and processes will need to continue to be supported as they are today. However,
FERC 881 creates a practical need to be able to share these ratings in a more structured way, implying that
some support for seasonal ratings makes sense in TROLIE, even if it is optional.

However seasonal rating interop is challenging, because the definition and meaning of each season differs
between grid operators. The definition for [seasons](../concepts.md#seasons) in the FERC 881 context is
quite flexible. While internally, grid operators may assign seasonal ratings to well-known named seasons
such as `Fall`, the practices around `Fall` ratings can differ significantly between grid operators:

* Assumed start and end dates can be different.
* The FERC order specifies only that they must be updated _at least_ annually. In practice, the times they may be changed can be different.

The diagram below illustrates an example of rating providers with different season definitions. Consider the challenges
for `Transmission Provider 1` to exchange seasonal ratings with `Ratings Provider A` and `Transmission Provider 2`:
![Complex, Interweaving Seasonal Schedules](../images/ComplexSeasonalSchedules.svg)

This decision record describes seasonal rating support in TROLIE.

## Decision

TROLIE will add support for a seasonal clearinghouse, using the same pattern as used by forecasted and
real-time ratings. Support for either accepting proposals or querying snapshots is technically optional,
although it is likely most Transmission Providers must support at least sharing
their snapshots of in-use seasonal ratings. In practice, clearinghouse implementations may take seasonal proposals,
seasonal ratings from modeling systems, seasonal ratings from other systems, or any combination of these into account.

The familiar TROLIE concepts of proposals,
snapshots and a clearinghouse have multiple benefits for seasonal ratings:

* While there are no EMS operator overrides or topology conditions to consider like there would be with AARs, there are still jointly-owned facilities and tie lines where multiple ratings may be submitted by different Ratings Providers.
* Some Transmission Providers may elect to manually validate proposed seasonal ratings before using them, as is common in existing practices. The distinction between proposal and in-use snapshot provides a discrete step in the overall data flow where such manual validation may be inserted if desired.


### Defining Seasonal Ratings by Date Instead of Season Names

Seasonal ratings in TROLIE will always be defined via start and end dates, rather than named seasons such
as `Fall` or `Summer`. This way, the definition of what a rating provider is
submitting or a transmission provider is presenting
can be more transparent and precise, and is not explicitly coupled to any one entity's
choices as to their season definitions.

The pre-defined "named" seasons that are included in proposal and snapshot definitions are included in headers,
but only provided as interop debugging hints.

### Alignment of Seasons and Flexibility of TROLIE Server Implementations
Defining seasonal ratings in terms of start and end dates creates great flexibility in the shape of seasonal ratings that may be exchanged.

However, the specification explicitly **does not** imply that TROLIE servers **must** accept
seasonal ratings of any arbitrary start and end date at any time. Transmission Providers
implementing TROLIE are ultimately free to decide how flexible they want to be.

For example, a Transmission Provider may choose only to accept seasonal ratings that
match that Transmission Provider's pre-defined season start and end dates. Proposals
for these seasons may then need to submitted before some cut-off time determined by
the implementer. Such proposals may be rejected using an HTTP 422 response, in
much the same fashion to forecasts.

TROLIE server implementations may reject proposals that do not adhere to the Transmission
Provider's business rules and practices.


## Consequences

Seasonal rating support is implemented in the TROLIE [specification](../spec#tag/Seasonal).
175 changes: 175 additions & 0 deletions docs/example-narratives/examples/seasonal-ratings-proposals-conditional.json
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,175 @@
{
"proposal-header": {
"source": {
"last-updated": "2025-10-31T15:05:43.044267100-07:00",
"provider": "UTILITY-A",
"origin-id": "5aeacb25-9b65-4738-8a00-ac10afa63640"
},
"default-emergency-durations": [
{
"name": "emergency",
"duration-minutes": 240
}
],
"power-system-resources": [
{
"resource-id": "8badf00d-145-in-service",
"alternate-identifiers": [
{
"name": "EMS.Name.145-in-service",
"authority": "TO-NERC-ID"
}
]
},
{
"resource-id": "8badf00d-145-out-of-service",
"alternate-identifiers": [
{
"name": "EMS.Name.145-out-of-service",
"authority": "TO-NERC-ID"
}
]
}
]
},
"ratings": [
{
"resource-id": "8badf00d-145-in-service",
"periods": [
{
"season-name": "WINTER",
"period-start": "2024-11-15T00:00:00-05:00",
"period-end": "2025-03-01T00:00:00-05:00",
"continuous-operating-limit": {
"mva": 160
},
"emergency-operating-limits": [
{
"duration-name": "emergency",
"limit": {
"mva": 165
}
}
]
},
{
"season-name": "SPRING",
"period-start": "2025-03-01T00:00:00-05:00",
"period-end": "2025-06-15T00:00:00-05:00",
"continuous-operating-limit": {
"mva": 160
},
"emergency-operating-limits": [
{
"duration-name": "lte",
"limit": {
"mva": 165
}
}
]
},
{
"season-name": "SUMMER",
"period-start": "2025-06-15T00:00:00-05:00",
"period-end": "2025-09-01T00:00:00-05:00",
"continuous-operating-limit": {
"mva": 160
},
"emergency-operating-limits": [
{
"duration-name": "lte",
"limit": {
"mva": 165
}
}
]
},
{
"season-name": "FALL",
"period-start": "2025-09-01T00:00:00-05:00",
"period-end": "2025-11-15T00:00:00-05:00",
"continuous-operating-limit": {
"mva": 160
},
"emergency-operating-limits": [
{
"duration-name": "lte",
"limit": {
"mva": 165
}
}
]
}
]
},
{
"resource-id": "8badf00d-145-out-of-service",
"periods": [
{
"season-name": "WINTER",
"period-start": "2024-11-15T00:00:00-05:00",
"period-end": "2025-03-01T00:00:00-05:00",
"continuous-operating-limit": {
"mva": 160
},
"emergency-operating-limits": [
{
"duration-name": "emergency",
"limit": {
"mva": 165
}
}
]
},
{
"season-name": "SPRING",
"period-start": "2025-03-01T00:00:00-05:00",
"period-end": "2025-06-15T00:00:00-05:00",
"continuous-operating-limit": {
"mva": 160
},
"emergency-operating-limits": [
{
"duration-name": "lte",
"limit": {
"mva": 165
}
}
]
},
{
"season-name": "SUMMER",
"period-start": "2025-06-15T00:00:00-05:00",
"period-end": "2025-09-01T00:00:00-05:00",
"continuous-operating-limit": {
"mva": 160
},
"emergency-operating-limits": [
{
"duration-name": "lte",
"limit": {
"mva": 165
}
}
]
},
{
"season-name": "FALL",
"period-start": "2025-09-01T00:00:00-05:00",
"period-end": "2025-11-15T00:00:00-05:00",
"continuous-operating-limit": {
"mva": 160
},
"emergency-operating-limits": [
{
"duration-name": "lte",
"limit": {
"mva": 165
}
}
]
}
]
}
]
}
Loading

0 comments on commit da622cc

Please sign in to comment.